1. Field of the Invention
The present invention relates to a heat developing apparatus in which a latent image of a heat developing photosensitive material is made visible by being heated thereby developing processing the heat developing photosensitive material.
2. Description of the Related Art
In addition to the photosensitive material that makes visible a latent image formed on the photosensitive material by a wet developing process using a processing solution such as developer, fixer or the like, a photosensitive material that makes visible a latent image by a dry developing process that does not use a processing solution has been used.
As one example of the dry developing process, the following heat- developing is generally carried out: the photosensitive material on which the image is formed by exposure and the image receiving material are superimposed, heated and pressed, thereby transferring the image according to the latent image formed on the photosensitive material by exposure to the image receiving material.
On the other hand, the photosensitive material that is developed by the dry developing process forms a photosensitive layer by using an emulsion that scatters silver halide acting as a photocatalyst, a silver salt acting as an image forming material, a reducing agent for silver ions, and the like within the binder. By heating such a photosensitive material to a predetermined temperature, the latent image formed on the photosensitive layer by exposure can be made visible (hereinafter, referred to a heat developing photosensitive material).
Generally, the heat developing apparatus, which carries out the heat-developing, is provided with a multiplicity of rollers disposed at a heating drum and at a peripheral portion thereof. In such a heat developing apparatus, the heat developing photosensitive material is entrained about the heating drum, while being pressed by the rollers. Then, the heating drum is rotated while the heat developing photosensitive material is nipped between the heating drum and the rollers, thereby transporting the heat developing photosensitive material while heating the heat developing material by the heat of the heating drum.
Examples of the heat developing apparatuses that simultaneously transport and heat the heat developing photosensitive material include a heat developing apparatus in which the heat developing photosensitive material is nipped and transported by multiple roller pairs and heated by heating means such as a heater or the like when the heat developing photosensitive material is passed between the rollers.
However, in some heat developing photosensitive materials, a photosensitive layer may swell and then harden due to heating. With such heat developing photosensitive materials, during heating, wrinkles may be generated because of the photosensitive layer being pressed by the rollers, and irregularities in density due to uneven heating may also be generated.
Especially, in the heat developing apparatus in which the heat developing photosensitive material is nipped and transported by the multiple roller pairs, the surface temperature of the heat developing photosensitive material in the state of being nipped by the rollers and the surface temperature thereof in the state of passing between the roller pairs are different from each other. Further, unless the heat developing photosensitive material is in a state of uniformly contacting a guide or the like, a difference in the surface temperature of the heat developing photosensitive material is caused between a portion which contacts the guide, and other portion which doses not contact the guide.
The deviation in the temperature causes irregularities in density of an image recorded on the heat developing photosensitive material, and when the heat developing photosensitive material is nipped by the rollers, wrinkles are generated in the heat developing photosensitive material due to elongation thereof caused by linear expansion. As a result, the finished quality of the image is deteriorated.